I started getting MP3’s from Amazon because they occasionally have promotions that allow you to download a few for free.
The Amazon MP3 Downloader conveniently automatically adds downloaded MP3’s to iTunes. After the MP3 is downloaded (typically in the Music/Amazon MP3 folder) a copy is made in the iTunes/iTunes Media/Music folder.
What is strange is that though the copy is the same size it is a different binary. I posted a question about this on Apple’s discussion site.
Also I noticed that iTunes has some music under its iTunes Music folder and some under its iTunes Media/Music folder. This is because iTunes 9 and later began using the iTunes Media/Music folder instead.
I decided I wanted everything under one folder so I used iTunes consolidate feature.
I then deleted the old iTunes Music folder after making sure everything was copied. I did notice that some of the copies were slightly different sizes.
Another unproductive way to spend a Sunday morning.